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flac_parser.c
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1 /*
2  * FLAC parser
3  * Copyright (c) 2010 Michael Chinen
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * FLAC parser
25  *
26  * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
27  * Each time it finds and verifies a CRC-8 header it sees which of the
28  * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
29  * that ends at the newly found header.
30  * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of its crc-verified
31  * children, penalized by changes in sample rate, frame number, etc.
32  * The parser returns the frame with the highest score.
33  **/
34 
35 #include "libavutil/attributes.h"
36 #include "libavutil/crc.h"
37 #include "libavutil/fifo.h"
38 #include "bytestream.h"
39 #include "parser.h"
40 #include "flac.h"
41 
42 /** maximum number of adjacent headers that compare CRCs against each other */
43 #define FLAC_MAX_SEQUENTIAL_HEADERS 3
44 /** minimum number of headers buffered and checked before returning frames */
45 #define FLAC_MIN_HEADERS 10
46 /** estimate for average size of a FLAC frame */
47 #define FLAC_AVG_FRAME_SIZE 8192
48 
49 /** scoring settings for score_header */
50 #define FLAC_HEADER_BASE_SCORE 10
51 #define FLAC_HEADER_CHANGED_PENALTY 7
52 #define FLAC_HEADER_CRC_FAIL_PENALTY 50
53 #define FLAC_HEADER_NOT_PENALIZED_YET 100000
54 #define FLAC_HEADER_NOT_SCORED_YET -100000
55 
56 /** largest possible size of flac header */
57 #define MAX_FRAME_HEADER_SIZE 16
58 
59 typedef struct FLACHeaderMarker {
60  int offset; /**< byte offset from start of FLACParseContext->buffer */
61  int *link_penalty; /**< pointer to array of local scores between this header
62  and the one at a distance equal array position */
63  int max_score; /**< maximum score found after checking each child that
64  has a valid CRC */
65  FLACFrameInfo fi; /**< decoded frame header info */
66  struct FLACHeaderMarker *next; /**< next CRC-8 verified header that
67  immediately follows this one in
68  the bytestream */
69  struct FLACHeaderMarker *best_child; /**< following frame header with
70  which this frame has the best
71  score with */
73 
74 typedef struct FLACParseContext {
75  AVCodecParserContext *pc; /**< parent context */
76  AVCodecContext *avctx; /**< codec context pointer for logging */
77  FLACHeaderMarker *headers; /**< linked-list that starts at the first
78  CRC-8 verified header within buffer */
79  FLACHeaderMarker *best_header; /**< highest scoring header within buffer */
80  int nb_headers_found; /**< number of headers found in the last
81  flac_parse() call */
82  int nb_headers_buffered; /**< number of headers that are buffered */
83  int best_header_valid; /**< flag set when the parser returns junk;
84  if set return best_header next time */
85  AVFifoBuffer *fifo_buf; /**< buffer to store all data until headers
86  can be verified */
87  int end_padded; /**< specifies if fifo_buf's end is padded */
88  uint8_t *wrap_buf; /**< general fifo read buffer when wrapped */
89  int wrap_buf_allocated_size; /**< actual allocated size of the buffer */
90  FLACFrameInfo last_fi; /**< last decoded frame header info */
91  int last_fi_valid; /**< set if last_fi is valid */
93 
94 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
96 {
97  GetBitContext gb;
98  init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
99  return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
100 }
101 
102 /**
103  * Non-destructive fast fifo pointer fetching
104  * Returns a pointer from the specified offset.
105  * If possible the pointer points within the fifo buffer.
106  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
107  * buffer is used.
108  * The pointer can be NULL. In any case it will be reallocated to hold the size.
109  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
110  * then the subsequent calls should pass in a different wrap_buf so as to not
111  * overwrite the contents of the previous wrap_buf.
112  * This function is based on av_fifo_generic_read, which is why there is a comment
113  * about a memory barrier for SMP.
114  */
116  uint8_t** wrap_buf, int* allocated_size)
117 {
118  AVFifoBuffer *f = fpc->fifo_buf;
119  uint8_t *start = f->rptr + offset;
120  uint8_t *tmp_buf;
121 
122  if (start >= f->end)
123  start -= f->end - f->buffer;
124  if (f->end - start >= len)
125  return start;
126 
127  tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
128 
129  if (!tmp_buf) {
130  av_log(fpc->avctx, AV_LOG_ERROR,
131  "couldn't reallocate wrap buffer of size %d", len);
132  return NULL;
133  }
134  *wrap_buf = tmp_buf;
135  do {
136  int seg_len = FFMIN(f->end - start, len);
137  memcpy(tmp_buf, start, seg_len);
138  tmp_buf = (uint8_t*)tmp_buf + seg_len;
139 // memory barrier needed for SMP here in theory
140 
141  start += seg_len - (f->end - f->buffer);
142  len -= seg_len;
143  } while (len > 0);
144 
145  return *wrap_buf;
146 }
147 
148 /**
149  * Return a pointer in the fifo buffer where the offset starts at until
150  * the wrap point or end of request.
151  * len will contain the valid length of the returned buffer.
152  * A second call to flac_fifo_read (with new offset and len) should be called
153  * to get the post-wrap buf if the returned len is less than the requested.
154  **/
156 {
157  AVFifoBuffer *f = fpc->fifo_buf;
158  uint8_t *start = f->rptr + offset;
159 
160  if (start >= f->end)
161  start -= f->end - f->buffer;
162  *len = FFMIN(*len, f->end - start);
163  return start;
164 }
165 
167 {
169  uint8_t *header_buf;
170  int size = 0;
171  header_buf = flac_fifo_read_wrap(fpc, offset,
173  &fpc->wrap_buf,
175  if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
176  FLACHeaderMarker **end_handle = &fpc->headers;
177  int i;
178 
179  size = 0;
180  while (*end_handle) {
181  end_handle = &(*end_handle)->next;
182  size++;
183  }
184 
185  *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
186  if (!*end_handle) {
187  av_log(fpc->avctx, AV_LOG_ERROR,
188  "couldn't allocate FLACHeaderMarker\n");
189  return AVERROR(ENOMEM);
190  }
191  (*end_handle)->fi = fi;
192  (*end_handle)->offset = offset;
193  (*end_handle)->link_penalty = av_malloc(sizeof(int) *
195  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
196  (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
197 
198  fpc->nb_headers_found++;
199  size++;
200  }
201  return size;
202 }
203 
204 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
205  int search_start)
206 
207 {
208  int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
209  uint32_t x;
210 
211  for (i = 0; i < mod_offset; i++) {
212  if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
213  size = find_headers_search_validate(fpc, search_start + i);
214  }
215 
216  for (; i < buf_size - 1; i += 4) {
217  x = AV_RB32(buf + i);
218  if (((x & ~(x + 0x01010101)) & 0x80808080)) {
219  for (j = 0; j < 4; j++) {
220  if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
221  size = find_headers_search_validate(fpc, search_start + i + j);
222  }
223  }
224  }
225  return size;
226 }
227 
228 static int find_new_headers(FLACParseContext *fpc, int search_start)
229 {
231  int search_end, size = 0, read_len, temp;
232  uint8_t *buf;
233  fpc->nb_headers_found = 0;
234 
235  /* Search for a new header of at most 16 bytes. */
236  search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
237  read_len = search_end - search_start + 1;
238  buf = flac_fifo_read(fpc, search_start, &read_len);
239  size = find_headers_search(fpc, buf, read_len, search_start);
240  search_start += read_len - 1;
241 
242  /* If fifo end was hit do the wrap around. */
243  if (search_start != search_end) {
244  uint8_t wrap[2];
245 
246  wrap[0] = buf[read_len - 1];
247  read_len = search_end - search_start + 1;
248 
249  /* search_start + 1 is the post-wrap offset in the fifo. */
250  buf = flac_fifo_read(fpc, search_start + 1, &read_len);
251  wrap[1] = buf[0];
252 
253  if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
254  temp = find_headers_search_validate(fpc, search_start);
255  size = FFMAX(size, temp);
256  }
257  search_start++;
258 
259  /* Continue to do the last half of the wrap. */
260  temp = find_headers_search(fpc, buf, read_len, search_start);
261  size = FFMAX(size, temp);
262  search_start += read_len - 1;
263  }
264 
265  /* Return the size even if no new headers were found. */
266  if (!size && fpc->headers)
267  for (end = fpc->headers; end; end = end->next)
268  size++;
269  return size;
270 }
271 
273  FLACFrameInfo *header_fi,
274  FLACFrameInfo *child_fi,
275  int log_level_offset)
276 {
277  int deduction = 0;
278  if (child_fi->samplerate != header_fi->samplerate) {
279  deduction += FLAC_HEADER_CHANGED_PENALTY;
280  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
281  "sample rate change detected in adjacent frames\n");
282  }
283  if (child_fi->bps != header_fi->bps) {
284  deduction += FLAC_HEADER_CHANGED_PENALTY;
285  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
286  "bits per sample change detected in adjacent frames\n");
287  }
288  if (child_fi->is_var_size != header_fi->is_var_size) {
289  /* Changing blocking strategy not allowed per the spec */
290  deduction += FLAC_HEADER_BASE_SCORE;
291  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
292  "blocking strategy change detected in adjacent frames\n");
293  }
294  if (child_fi->channels != header_fi->channels) {
295  deduction += FLAC_HEADER_CHANGED_PENALTY;
296  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
297  "number of channels change detected in adjacent frames\n");
298  }
299  return deduction;
300 }
301 
303  FLACHeaderMarker *header,
305  int log_level_offset)
306 {
307  FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
308  int deduction, deduction_expected = 0, i;
309  deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
310  log_level_offset);
311  /* Check sample and frame numbers. */
312  if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
313  != header_fi->blocksize) &&
314  (child_fi->frame_or_sample_num
315  != header_fi->frame_or_sample_num + 1)) {
316  FLACHeaderMarker *curr;
317  int expected_frame_num, expected_sample_num;
318  /* If there are frames in the middle we expect this deduction,
319  as they are probably valid and this one follows it */
320 
321  expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
322  curr = header;
323  while (curr != child) {
324  /* Ignore frames that failed all crc checks */
325  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
327  expected_frame_num++;
328  expected_sample_num += curr->fi.blocksize;
329  break;
330  }
331  }
332  curr = curr->next;
333  }
334 
335  if (expected_frame_num == child_fi->frame_or_sample_num ||
336  expected_sample_num == child_fi->frame_or_sample_num)
337  deduction_expected = deduction ? 0 : 1;
338 
339  deduction += FLAC_HEADER_CHANGED_PENALTY;
340  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
341  "sample/frame number mismatch in adjacent frames\n");
342  }
343 
344  /* If we have suspicious headers, check the CRC between them */
345  if (deduction && !deduction_expected) {
346  FLACHeaderMarker *curr;
347  int read_len;
348  uint8_t *buf;
349  uint32_t crc = 1;
350  int inverted_test = 0;
351 
352  /* Since CRC is expensive only do it if we haven't yet.
353  This assumes a CRC penalty is greater than all other check penalties */
354  curr = header->next;
355  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
356  curr = curr->next;
357 
361 
362  /* Although overlapping chains are scored, the crc should never
363  have to be computed twice for a single byte. */
364  start = header;
365  end = child;
366  if (i > 0 &&
367  header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
368  while (start->next != child)
369  start = start->next;
370  inverted_test = 1;
371  } else if (i > 0 &&
372  header->next->link_penalty[i-1] >=
374  end = header->next;
375  inverted_test = 1;
376  }
377 
378  read_len = end->offset - start->offset;
379  buf = flac_fifo_read(fpc, start->offset, &read_len);
380  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
381  read_len = (end->offset - start->offset) - read_len;
382 
383  if (read_len) {
384  buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
385  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
386  }
387  }
388 
389  if (!crc ^ !inverted_test) {
390  deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
391  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
392  "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
393  header->offset, header_fi->frame_or_sample_num,
394  child->offset, child_fi->frame_or_sample_num);
395  }
396  }
397  return deduction;
398 }
399 
400 /**
401  * Score a header.
402  *
403  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
404  * If it has children, (subsequent frames of which the preceding CRC footer
405  * validates against this one,) then take the maximum score of the children,
406  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
407  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
408  * because it can change often.
409  **/
411 {
413  int dist = 0;
414  int child_score;
415  int base_score = FLAC_HEADER_BASE_SCORE;
416  if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
417  return header->max_score;
418 
419  /* Modify the base score with changes from the last output header */
420  if (fpc->last_fi_valid) {
421  /* Silence the log since this will be repeated if selected */
422  base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
423  AV_LOG_DEBUG);
424  }
425 
426  header->max_score = base_score;
427 
428  /* Check and compute the children's scores. */
429  child = header->next;
430  for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
431  /* Look at the child's frame header info and penalize suspicious
432  changes between the headers. */
433  if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
434  header->link_penalty[dist] = check_header_mismatch(fpc, header,
435  child, AV_LOG_DEBUG);
436  }
437  child_score = score_header(fpc, child) - header->link_penalty[dist];
438 
439  if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
440  /* Keep the child because the frame scoring is dynamic. */
441  header->best_child = child;
442  header->max_score = base_score + child_score;
443  }
444  child = child->next;
445  }
446 
447  return header->max_score;
448 }
449 
451 {
452  FLACHeaderMarker *curr;
453  int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
454  /* First pass to clear all old scores. */
455  for (curr = fpc->headers; curr; curr = curr->next)
457 
458  /* Do a second pass to score them all. */
459  for (curr = fpc->headers; curr; curr = curr->next) {
460  if (score_header(fpc, curr) > best_score) {
461  fpc->best_header = curr;
462  best_score = curr->max_score;
463  }
464  }
465 }
466 
467 static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
468  int *poutbuf_size)
469 {
470  FLACHeaderMarker *header = fpc->best_header;
471  FLACHeaderMarker *child = header->best_child;
472  if (!child) {
473  *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
474  } else {
475  *poutbuf_size = child->offset - header->offset;
476 
477  /* If the child has suspicious changes, log them */
478  check_header_mismatch(fpc, header, child, 0);
479  }
480 
481  if (header->fi.channels != fpc->avctx->channels ||
482  !fpc->avctx->channel_layout) {
483  fpc->avctx->channels = header->fi.channels;
485  }
486  fpc->avctx->sample_rate = header->fi.samplerate;
487  fpc->pc->duration = header->fi.blocksize;
488  *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
489  &fpc->wrap_buf,
491 
492  fpc->best_header_valid = 0;
493  fpc->last_fi_valid = 1;
494  fpc->last_fi = header->fi;
495 
496  /* Return the negative overread index so the client can compute pos.
497  This should be the amount overread to the beginning of the child */
498  if (child)
499  return child->offset - av_fifo_size(fpc->fifo_buf);
500  return 0;
501 }
502 
504  const uint8_t **poutbuf, int *poutbuf_size,
505  const uint8_t *buf, int buf_size)
506 {
507  FLACParseContext *fpc = s->priv_data;
508  FLACHeaderMarker *curr;
509  int nb_headers;
510  const uint8_t *read_end = buf;
511  const uint8_t *read_start = buf;
512 
515  if (frame_header_is_valid(avctx, buf, &fi)) {
516  s->duration = fi.blocksize;
517  if (!avctx->sample_rate)
518  avctx->sample_rate = fi.samplerate;
519  }
520  *poutbuf = buf;
521  *poutbuf_size = buf_size;
522  return buf_size;
523  }
524 
525  fpc->avctx = avctx;
526  if (fpc->best_header_valid)
527  return get_best_header(fpc, poutbuf, poutbuf_size);
528 
529  /* If a best_header was found last call remove it with the buffer data. */
530  if (fpc->best_header && fpc->best_header->best_child) {
532  FLACHeaderMarker *best_child = fpc->best_header->best_child;
533 
534  /* Remove headers in list until the end of the best_header. */
535  for (curr = fpc->headers; curr != best_child; curr = temp) {
536  if (curr != fpc->best_header) {
537  av_log(avctx, AV_LOG_DEBUG,
538  "dropping low score %i frame header from offset %i to %i\n",
539  curr->max_score, curr->offset, curr->next->offset);
540  }
541  temp = curr->next;
542  av_freep(&curr->link_penalty);
543  av_free(curr);
544  fpc->nb_headers_buffered--;
545  }
546  /* Release returned data from ring buffer. */
547  av_fifo_drain(fpc->fifo_buf, best_child->offset);
548 
549  /* Fix the offset for the headers remaining to match the new buffer. */
550  for (curr = best_child->next; curr; curr = curr->next)
551  curr->offset -= best_child->offset;
552 
553  fpc->nb_headers_buffered--;
554  best_child->offset = 0;
555  fpc->headers = best_child;
557  fpc->best_header = best_child;
558  return get_best_header(fpc, poutbuf, poutbuf_size);
559  }
560  fpc->best_header = NULL;
561  } else if (fpc->best_header) {
562  /* No end frame no need to delete the buffer; probably eof */
564 
565  for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
566  temp = curr->next;
567  av_freep(&curr->link_penalty);
568  av_free(curr);
569  }
570  fpc->headers = fpc->best_header->next;
572  av_freep(&fpc->best_header);
573  }
574 
575  /* Find and score new headers. */
576  /* buf_size is to zero when padding, so check for this since we do */
577  /* not want to try to read more input once we have found the end. */
578  /* Note that as (non-modified) parameters, buf can be non-NULL, */
579  /* while buf_size is 0. */
580  while ((buf && buf_size && read_end < buf + buf_size &&
582  || ((!buf || !buf_size) && !fpc->end_padded)) {
583  int start_offset;
584 
585  /* Pad the end once if EOF, to check the final region for headers. */
586  if (!buf || !buf_size) {
587  fpc->end_padded = 1;
588  buf_size = MAX_FRAME_HEADER_SIZE;
589  read_end = read_start + MAX_FRAME_HEADER_SIZE;
590  } else {
591  /* The maximum read size is the upper-bound of what the parser
592  needs to have the required number of frames buffered */
593  int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
594  read_end = read_end + FFMIN(buf + buf_size - read_end,
595  nb_desired * FLAC_AVG_FRAME_SIZE);
596  }
597 
598  /* Fill the buffer. */
599  if ( av_fifo_space(fpc->fifo_buf) < read_end - read_start
600  && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
601  av_log(avctx, AV_LOG_ERROR,
602  "couldn't reallocate buffer of size %td\n",
603  (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
604  goto handle_error;
605  }
606 
607  if (buf && buf_size) {
608  av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
609  read_end - read_start, NULL);
610  } else {
611  int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
612  av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
613  }
614 
615  /* Tag headers and update sequences. */
616  start_offset = av_fifo_size(fpc->fifo_buf) -
617  ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
618  start_offset = FFMAX(0, start_offset);
619  nb_headers = find_new_headers(fpc, start_offset);
620 
621  if (nb_headers < 0) {
622  av_log(avctx, AV_LOG_ERROR,
623  "find_new_headers couldn't allocate FLAC header\n");
624  goto handle_error;
625  }
626 
627  fpc->nb_headers_buffered = nb_headers;
628  /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
629  if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
630  if (buf && read_end < buf + buf_size) {
631  read_start = read_end;
632  continue;
633  } else {
634  goto handle_error;
635  }
636  }
637 
638  /* If headers found, update the scores since we have longer chains. */
639  if (fpc->end_padded || fpc->nb_headers_found)
640  score_sequences(fpc);
641 
642  /* restore the state pre-padding */
643  if (fpc->end_padded) {
644  int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
645  /* HACK: drain the tail of the fifo */
648  if (warp) {
649  fpc->fifo_buf->wptr += fpc->fifo_buf->end -
650  fpc->fifo_buf->buffer;
651  }
652  buf_size = 0;
653  read_start = read_end = NULL;
654  }
655  }
656 
657  curr = fpc->headers;
658  for (curr = fpc->headers; curr; curr = curr->next) {
659  if (curr->max_score > 0 &&
660  (!fpc->best_header || curr->max_score > fpc->best_header->max_score)) {
661  fpc->best_header = curr;
662  }
663  }
664 
665  if (fpc->best_header) {
666  fpc->best_header_valid = 1;
667  if (fpc->best_header->offset > 0) {
668  /* Output a junk frame. */
669  av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
670  fpc->best_header->offset);
671 
672  /* Set duration to 0. It is unknown or invalid in a junk frame. */
673  s->duration = 0;
674  *poutbuf_size = fpc->best_header->offset;
675  *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
676  &fpc->wrap_buf,
678  return buf_size ? (read_end - buf) : (fpc->best_header->offset -
679  av_fifo_size(fpc->fifo_buf));
680  }
681  if (!buf_size)
682  return get_best_header(fpc, poutbuf, poutbuf_size);
683  }
684 
685 handle_error:
686  *poutbuf = NULL;
687  *poutbuf_size = 0;
688  return read_end - buf;
689 }
690 
692 {
693  FLACParseContext *fpc = c->priv_data;
694  fpc->pc = c;
695  /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
696  it drains. This is allocated early to avoid slow reallocation. */
698  if (!fpc->fifo_buf)
699  return AVERROR(ENOMEM);
700  return 0;
701 }
702 
704 {
705  FLACParseContext *fpc = c->priv_data;
706  FLACHeaderMarker *curr = fpc->headers, *temp;
707 
708  while (curr) {
709  temp = curr->next;
710  av_freep(&curr->link_penalty);
711  av_free(curr);
712  curr = temp;
713  }
714  av_fifo_free(fpc->fifo_buf);
715  av_free(fpc->wrap_buf);
716 }
717 
720  .priv_data_size = sizeof(FLACParseContext),
721  .parser_init = flac_parse_init,
722  .parser_parse = flac_parse,
723  .parser_close = flac_parse_close,
724 };